Shaft coupling



July 25, 1933. E K, LE FEVRE 1,919,437

SHAFT COUPLING Fle'd June 28, 1932 Edwin K. Leldre Patented .ul'y 25, 1933 UNI-TED STATIESk PATENT PFF EDWIN K. LE FnvR-nor Enemvroon, MARYLANnAssIeNoR To wnIcFrELn Enenalena@,`l

.ING COMPANY, F DISTRICT OF COLUMBIA, A COR'EORATEON OF DELAWARE SHAFT COUPLING Application ined rane as,

lThis invention relates to shaft couplings of that type which' automatically disengage the driving .and driven members at a predetermined overload value. y Y :y

Such couplings as usually constructed in. clude interdigitating members such asvsloping teeth which move outwardly upon one another progressively as the torque increasesy until they reaclrthe point of disengagement.-

The defect of such couplings is that forv any value of overloadless than that at which the coupling releases, the teeth remain engaged at less than their full deptlnftlius reducing the shear-resisting cross seotion'of the coupling as the torque increases, Aand i the load is carried by the end portions only y of the teeth, it vfrequently results. in the teeth being stripped..Y

The present invention obviates this defectA by holding the teeth positively in full depth engagement throughout the rise-in torque value, until the predetermined releasel value` has been attained. Y

This is accomplished by interposing a body'of incompressible liquid between the relatively movable walls ofa closed chamber, said chamber ,being so related to the teeth that it tends to contract in capacity as the teeth tend to move apart,'but is 'prevented from doing so by the presence of the incompressible liquid. The pressure of the torque is thus transmittedto the liquidwhich fills saidchainber, means being providedfso that when the torque exceeds the value predef termined as the release point of the coupling,

a componentofthe pressure of the liquid, of nedetermined small` value, acts to open an outlet for the liquidvhich escaping from the chamber permits the teeth suddenly and completely to unmesh.

The'invention of course contemplates the provision of means for restoringthe parts, including vthe displacedliquid,to normal operative relation. Y

Other-objects .of the invention will appear as the following description of alpr'e'ferredf land practical embodiment thereof proceeds.

In the drawing wl ich accompaniesv and forms a part of the following specificationA and throughout the several figures of which coupling.

1932. serial No. 619,782.

the same` characters of reference have been employed to designate identical parts,.i

Figure l .is a longitudinal section of a coupling embodying the principles of the, invention, the partsbeing shown A engaged relation; p

Figure. 2 is a similar disengaged". Y Y i Figure Bis a crosssection taken along the line 23e-8 of Figure 1. Y r Y vl `igure 4 is across section taken along 'the line 4-4'of FigureQ.- e Figure is aside elevation, partly in section showing the meshing 1 Figure vvhis afragnientary-view partly in section showing a modified detail of the invention.v .n f' Referring now in detail tothe several: figures and first adverting to'that groupfin- View, the parts being 'y vteeth of the,

cluding Figures l and 2 and 5, the numerals l and Zrrep'resent. thev driving and driven shafts each of which is provided with a disclilre head 3 and ,4, respectivelyv which aswill presently be seen function as pistons, and are preferably of the same diameter. c

. The shaftQ is provided adjacent vthe head 4 with aseries of longitudinalsplines 5 and said shaft is provided with an extension 'in the form o f a sleeve 'cylinder 6 having a head 7 formed with spline grooves receiving the splines 5 and by means of which `the-cylinder G is slidably mounted on the straf-512. i i

The shafts l and-2 are in alignment, the 'Y 85.v

cylinder 6 embracing bothpiston/heads 3 and 4. Thefouter face of thepiston head 3 is' providedwith an annular seriesof teeth 8 and the adjacent endv of l*the cylinder yisl closed by a cylinder head 9 slidable onzthe" shaft .l and. being provided Wit-hiteethvl()Y with' Whichthe teeth 8 onthe piston head T3 interrnesh." It will be understood that when the cylinder k6 is slid in a leftward direction i with reference to Figures l and2 the :teeth i lare .disengaged so that the shaftgl together with the 'piston head visyfreed fronii'thel shaft Q'a-nd its extension, thecylinder 6, thisl positionof the parts being shown in Figure 2,'and that when the cylinder 6 is moved e i to the'right the teeth are brought into en-V gagement and the driving and driven shafts Aare coupled.

AFigure 5sliows that the teeth 8 and 10 have sloping faces on both sides. vIt is obvious that in the absence of any other mechanism than has been described up to this point, the driving torque will tend progressively to-separate the driving and driven teeth, the sloping sides of one series sliding outward against the sloping sides of the other series. i i I In the illustrated embodiment of the invention the teeth slope on both sides,`indieating that the coupling disengages in response to overload in either direction of rotation. The cylinder heads 7 and 9 may be secured in any suitable manner.' They are here shown as being screwed intothe respective ends of the cylinder, and held in placed by deeply imbedded set screws 11.

vNormally the cylinder (3 is biased in a direction to keep the teeth 8 and 10 enineshed, by a spiral spring 12 held incompression between the Vouter face of the piston head el, and the head 7 of the cylinder.

The construction of the couplingis such that the piston heads 3 and 4 are' spaced apart a definite and lixeddistance and that the. cylinder 6 has a septum oi'V partition 1.3 adapted to traverse said space when the cylinder 6 is slidably operated. rl`he piston heads 3 and d are providedwith cup leathers 14 and 15V or their equivalent, making the space between the piston heads a fluid tight chamber, and -the partition 13 has an aperture 16 closed by a transfer valve 23, the' latter being normally held to itsseat by a light leaf spring'24 or its equivalent, said aperture permitting the passage of fluid in said chamber from one side of said iartition to the other in certain phases of operation ofthe device. The fluid employed may be' any desirable incompressible liquid, such vfor example as water or oil.

It is apparent from an inspection of Figure 1 thatV if the spacebetwe-en the piston heads, and'which will henceforthbe designated as the chainberl?, were empty, the sole means for holding the teeth inv engagement would be the spring 12, and that a torque value tending to cause the `teeth to rid-e out upon one another to a position -of-disengagement would be yieldingly resisted by said spring alone, so that the teeth would progressively disengage, being open to the v. objection noted in connecti on with the statement of the, objects of the invention.

The present invention contemplates the i .illingof the chamber 17 with the incomtek pressible liquid, through the. screw-closed.

aperture 18 while the parts were in position shown in Figure 2. It will be noted that .the partition 13 abuts the head of the screw 19 which secures thexcup-leather to the piston head and thus determinesthe definite volume forces open the ball valve 20 and permits liquid on the right handof the partition 13 to flow through to the opposite side of the partition. The cylinder 6 is slid in the manner indicated until the screw 21 which secures the cup leather 15 in position abuts against the partition 13, or. some element secured thereto, as indicated in F igure 1. The rela.- tion of thehead of the screw 21y to the pai'- tition 13 is such that when the twoelements are in contact the teeth 8 and 10 are enmeshed to their full depth. The valve 2O is normally maintained seated by means of a leaf spring 22 or. its equivalent` secured tosaid partition, and the pressure of which spring is i ust sufficient to overcome the weight of thevalve 20 and the thrust of the spring 12. f

Assuming that the teeth are enme'slied as shown in Figures land 5, the rising value of the drivingtorque will tend to causathe teeth to iide out upon one' another, but thistendency can not be developed into actual movement of said teeth since the chamber 17 is a closed chamber and filled with a body of incompressible liquid. 4In consequence therefore, although the driving torque acting against the pressure'of spring 12 would ordinarily cause the teeth to at least partially disengage any such movement of said teeth is inhibited by the presence of the liquid. It will be understood that while the liquid is in a static condition within the chamber 17 as indicated vin Figure 1, the component of the driving torque which would move the teeth 1n an axial direction imposes a pressure upon `Examining the liquid. in the chamber 17. said chamber one-will observe that its opposite walls are of different area, the wall repiesented by the cup leather. 14 being circular, and in areabeing the entire cross section of the cylinder 6, while the oppcsite wall represented by partition 13 ,is equal to'this arca' less the area of the aperture 16.`

In the Vposition of parts shown in Figure 1,

the valve 23 being against-the piston 4 becomes for the time, virtually a part of said piston and not a part of the partition, soA that.

the eective fluid pressure at anytime upon said partition is the pressure upon the annular areaof said .partition not including the pressure upon said/valve.

Now, the pressure which is built up be-y tween the piston 3 4and the partition `by the torque is derived from' the mechanical force" tending to separatethe teeth ,8 and 10, that is to say, the force tending to draw the cylinder to the leftward as viewedin Figure l.

Now,- the value of thisforce is equal to the pressure against the circular wall of the piston 3 and is therefore greater than the force on `the partition 13. Consequently, we have an unbalanced force, the mechanical force acting at the teeth to move the cylinder to the leftwardbeing greater thanthe force acting upon the partition-to hold the cylinder in its t right-ward position. Consequently, the cyli inder will move to the left inst-vas soon as the differential between-these forces exceeds the pressure value acting upon the area of the aperture 16, reaches a point at which the pressure of the spring 12 is overcome. `Up' to this time, all move-ment of the-cylinder is inhibited by the incompressible fluid in the chamber 17, and therefore the teeth 8 and 10- remain enmeshed to their-fulldepth.

NVhen once disengaged,the driving and driven elements will run free, there beingno return of the liquid until the valve 2() has been opened bythe manual or otherwise mov-- ing ofthe cylinder 6 Vinto teeth enga D relation.

ring

In Figure 6 a slight modification of the invention is shown in which tliejfree valve 23 already described, is substitutedby a projection-25 integral with, or in any suitable manner made fast to the piston head l and having a valve lface 26 which seats upon the wall ofthe aperture 16. When the pressure upon the valve end of said projection becomes sufficient to contract the spring 12 and permit the cylinder to slide towards release position of the coupling, the aperture 16 is opened. This construction obviates the needof providing the return valve or its equivalent.

` It will 'be understood from the above description that I have invented an automatic coupling released by a torque value repre-v senting a predetermined overload in'which the movement towards release position does not tak-e place progressively but only wheii spring is multiplied by the ratio which the area of the partition 13 bears to the much smaller area of the aperture 16.

It is understood that the details of construction as shown and described, are merely byway of example and are by no means to be considered as limitingv the scope of the inven- 4 tion as definedby the termsof the appended claims.

. VVhatI claim as my invention is: 1

E1.V Shaft coupling comprising driving and driven shafts,intermeshing teeth connectingv` said shafts, said teeth being so shaped that a componentof thedriving torque tends to y force them apart,lav spring for lyieldingly holding said teeth in engagement, hydraulic i means `normallyfstatically impounded between said teethr and yspring for storing. the

said component ofthe 'driving torque, and Y means responsive `to a. component of a pre'- deterniined. pressure built up lin said `iinpounded means i-for overwhelmingthe. tensionof saidspring and unbalanc-ing the-static pressure of` said hydraulic means inv a direction to cause immediate andV complete disengagement ofthe teeth of l,said coupling. 2. Shaft coupling comprising driving and,

driven "shafts, a sleevesplined on one'shaftv and rotatably embracing they other, interfmeshing'teeth on said sleeve and the last named shaft so shaped that a component of the driving torque tends to force themapart, saidV teeth being engaged or 'disengaged by thefs'liding ofsaid sleeve in one or the other` direction, a spring normally `holding ksaid sleeve in the position in which said teeth are engaged, means defining Vwith said sleeve a chamber between said shafts, said'sleeve having a partition in said chamber biased to one side thereof by said spring, said partition being formedl With an aperture, making the area of said partition slightlyilessthan the;`

area of the opposite `wall ofsaidchamber, an

outwardly opening valve normally closing said aperture under pressure r`of said spring,

said chamber being filled Vwith an incompressible liquid normally in static statefor positivelyliolding said sleeve in teeth-engaging position, said'valve being adapted-to open when the-differential of. the lpressure iinpressed upon the incompressible liquid, between the I partition and, the opposite .wall of said chamberwrisesto avvalue sufficient to overcome said spring, permitting the disother side of said partition, whereby thel iinmediate and completedisengagement of said teeth takes place.

driven shafts, a'cylinder havingheads at its opposite ends, one head being splined on one.

3. Shaft coupling comprising driving and :no l placement ofthe hitherto static liquid to the Y shaft and the other head rotatably embracf ingthe other shaft, )iston heads at the endsof said shafts co-acting with the walls of said cylinder `and spaced apart, intermeshing teeth on the inner face of one cylinder head and the outerfface of the adjacent piston -i head, said teeth being so shaped that a component of the driving torque tendsto force them apart,'said teeth being engaged or disengaged bythe sliding of said cylinder in one or the'other direction, a spring normally holding said cylinder in the position in vwhich said teeth arev engaged, said piston heads and cylinder defining la chamber between said shafts, said cylinder having a partition in said chamber acting asa piston, and normally biased to one side of said chamber by said spring, said partition being formed with an aperture, making thearea of said partition slightly less than the area of the opposite wall of said chamber, an outwardly opening valve normally closing said aperture under pressure of said spring, said chamber being illed with anincompressible liquid normally in static state, for positively holding said cylinder in teeth-engaging position, said. valve being adapted to lopen when the differential of the pressure impressed upon said' incompressible, liquid, between the partition and the opposite wall of said'chamber, rises to a value sufiicient to overcome said spring, permittingthe displacement of the Vhitherto static liquid to the other side of said partition, wherebythe immediate and complete disengagement of said teeth takes place. A e

4. Shaft couplingas claimed in claim 3 the spring abutting the inner face of the splined cylinder head and the outer 4face ofthe adjacent piston head. i

5. Shaft coupling as claimed in claim 3 including a positive stop on the piston head having the teeth, for limiting the teeth-disengaging movement of said cylinder. j

6. Shaft coupling as claimed in claim Q includinga' return valve for restoring the liquid to the opposite sideof said'partition when said cylinder is slid to `teeth engaging position.

7. Shaft coupling as claimed in claim -2 said valveV comprising a fixed projection against which the walls'of the aperture in said partition are normally forced by the tension of said spring. y

8. Shaft coupling comprising drivingand driven Lshafts axially aligned and spaced apart, having diametrically enlarged piston heads attheir adjacent ends, a cylinder slidably embracing' said piston heads defining between them a chamber, cylinder heads at the ends of said cylinder, one splinablyvsecured -to one of said shafts whereby the cylinder becomes an extension of that shaft, and the other cylinder head rotatably embracing the other shaft behind its piston head, col acting teeth on last named piston vhea-d and the adjacentfface of the lastnamed cylinder head, a spring housed between the opposite cylinder head and its adjacent pistonA head, normally holdingV said cylinder 'yieldingly in teeth-engaging position, said teeth having sloping faces whereby a component ofthe driving torque tends to force the teeth apart,- said cylinder being provided with a partition in said chamber forming a movable wall for saidchamber, vsaid chamber being filled with-an incompressible liquid between saidv partition and the piston head havingthe teeth, for positively holding said cylinder in teeth-engaging positioniwhile said liquid is in static state, said partition being formed with an aperture making the area of said partition exposed to the incompressible liquid slightly less than the areav of the opposite piston head, a valve closing said aperturefeX-l teiorally under pressure of said spring and adapted toopen when the differentialV of thev pressure between the opposite walls ofsaid chamber rises to value suliicient to overcome said sirino oerniittino the dis )l-acenient of the hitherto static liquid to the other Vside of :said chamber, whereby immediate and' complete disengagement of said teeth takes place. y l

Y 9. Shaft coupling as claimed in claim 2 in-` cluding a return valve carried by said partition for restoring the liquid to the opposite side of said partition when said cylinder is moved to teeth-engaging position, and means kfor normally-holding said valve closed against kback pressure of said spring while said teeth are disengaged.v 1 v lO. Shaft coupling as claimed 1n claim 2,

` said Vvalve comprising a fixed projection against which the walls kof the aperture in said partition are normally'forced by the `tension of said spring, andxareturn valve opening .oppositely from the aforementioned valve for permitting return of the liquid to .the opposite side of said partition when the cylinder is moved to teeth-engaging position. ll. Shaft coupling comprising driving and driven shafts,an axially slidable cou-V pling element forming an extension of one sliaft, said slidable coupling element' and the other shaft having inter-.engaging over-load released elements, and fluid pressure means for inhibiting any torque-*induced releasing movement of said inter-engaging. elements until the over-load value has vbeen attained.

.EDlV-IN K. LEFEVRE.

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